Treatment of iron or steel



252. COMPOSITIONS,

Patented May 20, 1930 UNITED STATES Examine.

PATENT OFFICE KARL B. THEWS, OF DREXEL HILL, AND JOSEPH S. CARLITZ, OF PHILADELPHIA, PENNSYLVANIA; SAID CARLITZ ASSIGNOR T0 SAID THEWS TREATMENT OF IRON OR STEEL 1T0 Drawing. Application filed December This invention relates to a process for reducing the dissolution of iron and steel during the removal of iron oxide or scale in pickling baths of sul huric or other acids. The methods disfl'os e d erein are also useful in preventing corrosion of iron and steel containers of such acids.

Heretofore it has been customary to use various inhibiting agents in the pickling baths to prevent pitting or etching of the surface of the iron or steel. These substances have been more or less successful in the attainment of such results, the best of these inhibitors so far used apparently being the substitution products of normal thiourea of which the ditolyl derivatives are the most effective.

It is the object of this invention to improve the processes heretofore used by the use as inhibitors of derivatives .ofselenillir and tellurium which are found to be generally superior to the corresponding sulphiii derivatives.

The attainment of the object out-lined above and the more specific objects of the invention will be clear from the following description.

It is found that a greatly improved inhibiting action results if instead of the derivatives of normal thiourea, there are used derivativesof normal selenoureav or tellurourea. The derivatives include compounds having the general formula:

in which X represents either selenium or tellurium and R represents hydrogen, or an alkyl, aryl or acyl group, or in which two Rs may be replaced by an ethylene, or the like, derivative connected by two bonds to the same or different nitrogen atoms.

As examples of suitable alkyl groups, there may be cited methyl, ethyl, propyl, butyl,

7, 1929. Serial No. 412,565.

amyl, etc., propyl, butyl, amyl and higher radicals being of any of the various isomeric types, such as normal, iso-, tertiary, etc. Substituted alkyl groups may also be used, in which, for example, one or more hydrogen atoms are replaced by amino, sulphonic, nitro, or other groups.

The aryl groups may be j oincd to the nitrogen atoms either at the nucleus or side chain. Of the first type, phenyl, tolyl, Xylyl, a or ,8 naphthyl, etc. are examples. The junction to the nitrogen atoms may take place at any of the unsubstituted carbon atoms. Of the second type, benzyl is the best example. Here again there may be various groups replacing the hydrogen atoms in either the nucleus or sidehchainls. f

T e c s may be ormyl, cet l ropionyl, b enzoyl, phthalyl, succin yaf tf or substituted derivatives thereof.

While only one monosubstitution derivative of either normal selenourea or normal tellurourea may be formed, it Will be obvious from the structural formula given above that either 1, 2 or 1, 3 distribution products may be formed depending upon whether the substituent groups are in the same or different amino groups. The two substituents may be either the same or difierent; if different both may be of alkyl, aryl or acyl types or they may be of different types: for example, 1- methyl 3-p-tolyl selenourea, and 1,2 dibenzyl tellurourea are disubstitution products illustrative of these types.

As to trisubstitution products, it is necessary that two of the substituent groups be attached to one nitrogen atom and one to the other. Of these groups all may be the same, two the same, or all different and of the same or different types. Similarly, where there are four substituent groups, there may be duplication or all may be different.

There may also be used derivatives in which the two nitrogen atoms are joined to a single radical, each by a single linkage, or in which one of'the nitrogen atoms is joined to a radical by a double linkage. The radicals in these cases may be either alkyl, aryl, or acyl. As an example there may be cited the phthalyl derivative cs co N c0 ClH| It will be seen that this compound may be a considered to be a derivative of phthalimide. An analogous derivative of succinimide is an example of an aliphatic acyl derivative. An ethylene, propylene or similar radical may enter a similar position to form an alkylene derivative. The different nitrogen groups may be joined to the bonds of a bivalent radical such as phthalyl, succinyl, ethylene, or propylene. It will be understood that where go the term alkyl is used, it is in a broad sense so as to include not only alkylene groups, such as ethylene, but also heterocyclic derivatives such as terpene grou s. The terms aryl and acyl are intende to have similar broad T interpretations, the term aryl, for example,

being intended to include aralkyl such as benzyl.

In a general way, it may be said that the operative substances are represented by the general formula above in which one or more of the Rs represents an organic radical or hydrogen, and in which X represents Se or Te. It appears that the inhibiting action to a greater or less degree is characteristic of this class of compounds.

The mechanism of the rocess involved in usin these substances is similar to that usua 1y used. The pickling solution may contain SW5: other suitable acidic materials suc as ow used in eiiective concentrations. For example, approximately 10% sulphuric acid solution in water may be used. To such pickling solution up to approximately 1% of one of the inhibiting a ents is added. The pickling is then eflected in the usual fashion by submerging the iron or steel articles in the solution either at ordinary or elevated temperatures. In cases where it is desired to protect a tank against acid which is contained therein, the inhibiting agent is added to the acid.

While the derivatives are by far the most effective, normal selenourea and normal tellurourea both exert an appreciable inhibiting action and they are therefore considered to be within the scope of the invention. Of the various derivatives, the alkyl and aryl are generally found to be best; the acyl derivatives are less efl'ective but more so than the corresponding thiourea derivatives.

For convenience in handling the inhibiting substances in the small quantities necessary in a pickling bath, it may be desirable to mix them with a large proportion of a .5 carrier substance which may be of such nature as to assist the picklin action, for example, sodium chloride or so ium bisulphate. Mixtures of various inhibiting agents may also be used.

The various derivatives referred to are best prepared by the general methods well known to the art. In general it may be stated that the selenoand tellurourea derivatives are prepared similarly to the corresponding thiourea derivatives although special methods of preparation are well known to the art. In view of the fact that the preparations of the derivatives form no part of the instant invention, they have not been discussed in detail.

What we claim and desire to protect by Letters Patent is:

1. An aqueous solution of a non-oxidizing acid capable of dissolving iron oxides to .Which has been added an inhibitor comprising an organic substitution product of CX(NH in which X represents Se or Te.

2. An aqueous solution of an non-oxidizing acid capable of dissolving iron oxides to which has been added an inhibitor comprising an organic substitution product or selenourea.

3. An aqueous solution of a non-oxidizing acid capable of dissolving iron oxides to which has been added an inhibitor comprising a substance having the general formula CX(NR- in which X represents Se or Te, and R represents hydrogen or an alkyl, aryl or acyl group.

4. An a ueous solution of a non-oxidizing acid capa le of dissolving iron oxides to which has been added an inhibitor comprisin a substance having the general formula Ce (NR in which R represents hydrogen, or an alkyl, aryl or acyl group.

5. The process of pickling iron and steel products which consists in treating said products with an aqueous solution of a non-oxidizing acid capable of dissolving iron oxides to which has been added an inhibitor comprising an organic substitution product of CX(NH in which X represents Se or Te.

6. The process of pickling iron and steel products which consists in treating said products with an aqueous solution of a non-oxidizing acid ca able of dissolving iron oxides to which has een added'an inhibitor comprising an organic substitution product of selenourea.

7. The process of pickling iron and steel products which consists in treating said products with an aqueous solution of a non-oxidizing acid ca able of dissolving iron oxides to which has een added an inhibitor comprising a substance having the general formula CX(NR in which X represents Se or Te, and R represents hydrogen or an alkyl, aryl or acyl group.

8. he process of pickling iron and steel products which consists in treating said prodnets with an aqueous solution of a non-oxidizmg acid capable of dissolving iron oxides to which has been added an inhibitor comprisa substance havin the general formula (NR2) 2, in which KARL B. THEWS. JOSEPH s. GARLITZ.

Patent No. l, 759, 634.

represents hydrogen,

CERTIFICATE OF CORRECTION.

Granted May 20, 1930, to

KARL B. THEWS ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Page 2, line 88, claim 2,

for the word "an" second occurrence read "a", and line 91, for "or" read "of";

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 24th day of June, A. D. 1930.

(Seal) 

